Device for the continuous longitudinal seam welding of tubes

ABSTRACT

A device for the continuous longitudinal seam welding of tubes particularly by electron beam welding, includes a pair of opposed rollers arranged with their mating groove portions in opposition on a bracket which may be rotated so as to shift the rollers in transverse directions. The arrangement includes means for scanning the strip edges of a sheet material which is fed and formed into the form of a slotted tube and adjusting the edges so that the tube is fed between the rollers with the longitudinal groove or slot centered therebetween. The scanning elements are arranged along the strip edges to be welded and actuate a control for a motor which is employed for shifting the grooved rollers with the tube in order to control the position of the weld seam for the purpose of centering the seam in respect to the electron beam. In a preferred arrangement the workpiece is guided by pressure rolls arranged on respective opposite sides of the workpiece which are advantageously carried on a rocker arm so that they may be jointly pivoted about the axis of the workpiece. A second pressure roll pair for guiding the workpiece is advantageously arranged on the rocker arm at a location between the contactless scanning device and the welding pressure roll pair. The second pressure roll pair forces the two band edges of the sheet to be formed firmly together and firmly grips the workpiece running therebetween in the same manner as the welding pressure roll pair.

(.tvacan vXR 396489007 United States Patent Oppermann et al.

[ 1 Mar. 7, 1972 DEVICE FOR THE CONTINUOUS LONGITUDINAL SEAM WELDING OFTUBES lnventors: Willi Oppermann, Duisburg; Egon Schonitz, Rheinhausen;Werner Wagner, l-lomberg, all of Germany DEMAG Aktiengesellschatt,Germany Filed: May 7, 1970 Appl. No.: 35,386

Assignee: Duisburg,

US. Cl ..219/59, 219/121 EB, 219/125 R, 228/45 Int. Cl. ..B23k 31/06Field of Search ..219/124, 125, 126, 59, 60, 219/61, 121 EB;228/4S,9

References Cited UNITED STATES PATENTS Von Voros ..219/125 PrimaryExaminer-J. V. Truhe Assistant Examiner-L. A. Schutzman Attorney-McGlewand Toren [57] ABSTRACT A device for the continuous longitudinal seamwelding of tubes particularly by electron beam welding, includes a pairof opposed rollers arranged with their mating groove portions inopposition on a bracket which may be rotated so as to shift the rollersin transverse directions. The arrangement includes means for scanningthe strip edges of a sheet material which is fed and formed into theform of a slotted tube and adjusting the edges so that the tube is fedbetween the rollers with the longitudinal groove or slot centeredtherebetween. The scanning elements are arranged along the strip edgesto be welded and actuate a control for a motor which is employed forshifting the grooved rollers with the tube in order to control theposition of the weld seam for the purpose of centering the seam inrespect to the electron beam. in a preferred arrangement the workpieceis guided by pressure rolls arranged on respective opposite sides of theworkpiece which are advantageously carried on a rocker arm so that theymay be jointly pivoted about the axis of the workpiece. A secondpressure roll pair for guiding the workpiece is advantageously arrangedon the rocker arm at a location between the contactless scanning deviceand the welding pressure roll pair. The second pressure roll pair forcesthe two band edges of the sheet to be formed firmly together and firmlygrips the workpiece running therebetween in the same manner as thewelding pressure roll pair.

7 Claims, 7 Drawing Figures Patented March 7, 1972 3,648,007

3 Sheets-Sheet 1 IN V E N T 0R 5 w/u/ UPPffiMA/VN 660M scnamrz WERNERWAGNER f/Ie/r ATTORNEYS Pnnted March 7, 1972 3,648,007

3 Sheets-Sheet 3 INVENTORS W/LL/ OPRERMANA/ EGON scwdmrz WERNER WAGNEPflar A wan/v5 45 DEVICE FOR THE CONTINUOUS LONGITUDINAL SEAM WELDING OFTUBES SUMMARY OF THE INVENTION This invention relates in general towelding apparatus and in particular, to a new and useful continuouslongitudinal seam welding device for welding tubes by means of anelectron beam welding with improved means for centering guiding rollersfor the sheet material which may be shifted so as to center the seam inrelation to the electron beam.

The invention particularly relates to the longitudinal seam welding oftubes by electron beam welding and to an improved apparatus for guidingthe edges of the strip used for the manufacture of the tube so that theseam may be centered in respect to a focused electrical energy of thebeam welder in order to form a seam of relatively small cross section atthe welding point. It is know for such purpose to use guiding tongues orguide rollers for the guidance of the slotted tube forming sheet. Eachguide tongue naturally slides along the edges of the strip and cantherefore easily damage it. The friction caused thereby also has adetrimental effect and such damage leads to welding faults. In addition,the accuracy of the forced guidance is in the range of millimeters.Because the area cross section of the electron beam for welding purposesis very small most accurate guidance of the sheet material and thelongitudinal seam is important.

In accordance with the present invention, means are provided forcontrolling the welding point without danger of damaging the strip edgein such a manner that a deviation from the centerline can be regulatedimmediately and most accurately in order to provide a precise centeringof the abutting edges of the formed sheet material for the purpose ofapplying a longitudinal welding seam by an electron beam.

The workpiece may be moved laterally about a pivot axis of the bracketwhich may be arranged parallel to the workpiece axis to permit thepressure rollers to counteract any migration of the band edges duringthe welding process. In the longitudinal seam welding of relativelythick-walled tubes, especially those with a large diameter, difficultieswill occur because, during the regulation of the band edge migration,the workpiece axis is pivoted out of the plane of the electron beam.

Thus, the band edge faces, which are pressed together by the weldingpressure rolls and directed radially toward the workpiece axis, areinclined the more, in relation to the electron beam, the greater thepivotal bracket movement necessary for pivoting the pressure rollers forthe necessary amount to effect the correction of the seam run. As theelectron beam is extremely narrow in many cases, for example, if thewelding edge plane is inclined in relation to the electron beam by 5 to7, an equally good welding from the outside inwardly is no longerinsured.

The present invention provides a mounting for pressure forming rollersfor pivotal movement about an axis which corresponds to the workpieceaxis in order to provide a simple means for insuring that the weld seamremains uninfluenced even with the correction of a maximum longitudinalseam migration which generally amounts to up to ill/2. By mounting thepressure rollers so that they can be pivoted about the workpiecelongitudinal axis, the workpiece can be rotated about the longitudinalaxis by the rollers by the same degree of the seam or band edgemigration but in an opposite direction of rotation. Thus, the weldingwill be uninfluenced by the degree of scam migration and the workpieceaxis will always lie in the plane of the electron beam. In addition, theexterior as well as the interior seam edges will always stay in thisplane, so that even at a relatively great seam migration the quality ofthe thick weld seam will remain the same as would be the case with anexact centering of the seam.

The simple apparatus for mounting the pressure rolls for pivotalmovement about the axis of the workpiece comprises a rocker armconstruction having end hub-portions or bosses which are pivotable aboutthe longitudinally spaced supporting pedestal journals on an axis whichcorresponds to the axis of the workpiece. In this case, a secondpressure roll pair for guiding the workpiece is advantageously arrangedon the arm between the welding pressure roll pair and the scanningdevice or centering means for locating the edges of the sheet which isto be formed into the tube. This second pressure roll pair lays the twoband edges against one another and firmly grips the workpiece runningthrough in the same manner as the welding pressure roll pair, thecombined roller action being such that it rotates the workpiece backinto the required position with certainty even at great seam migration.

The pivoting of the rocker arm which supports the two sets of rollers isadvantageously accomplished by a hydraulic drive, which can becontrolled accurately and very quickly. The device insures satisfactoryweld seams even at great working speeds which, with todays machinesextend to about 20 meters per minute.

An object of the invention is to provide an improved welding devicewhich includes means for scanning the position of two opposite edges ofa rolled sheet which is fed between forming rollers or pressure rollers,the rollers being mounted on a rocker arm together with at least oneother roller set and being movable with the rocker arm for pivotalmovement about an axis corresponding to the axis of the workpiece inorder to maintain a centering of the edges in respect to a weldingdevice.

Accordingly, it is an object of the invention to provide an improvedwelding device which includes means for scanning the position of twoopposite edges of a rolled sheet which is fed between forming rollersand for actuating a motor control in accordance with the sensedinformation for shifting the two rollers in order to maintain acentering of the edges in respect to a welding device.

A further object of the invention is to provide a welding apparatuswhich is simple in design, rugged in construction, and economical tomanufacture.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a front elevational view of a tube-forming and tube-weldingmachine constructed in accordance with the invention;

FIG. 2 is a side elevational view of the machine shown in FIG. 1;

FIG. 3 is a top plan view of the machine;

FIG. 4 is an enlarged somewhat schematic top plan view indicating thesensing device constructed and arranged in accordance with theinvention;

FIG. 5 is a front view of another embodiment of the invention;

FIG. 6 is a section taken along the line VI-Vl of FIG. 5; and

FIG. 7 is a longitudinal sectional view for the portion of the rockersfor the roller sets indicated in FIG. 5.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to thedrawings in particular, the invention embodied therein comprises awelding device generally designated 20 which includes a table or stand22 having spaced fonning and deflecting rollers 3 and 3' rotatablymounted thereon for rotation about substantially vertical axes atlocations to define a tube engaging nip 24 therebetween. A sheetmaterial 12 is formed by forming means (of which only rollers 3, 3' areshown) into a slotted cylinder 2. The cylinder 12 includes edges 11which bound a longitudinally extending slot 9 which is centered in thenip 24 between the rollers 3 and 3. The slot 9 is advantageouslycentered at a location directly beneath an operating welding part suchas an electron beam 1 of a welding device 28.

In accordance with a feature of the invention, the rollers 3 and 3 aresupported for rotation on a roller bracket 4 which has a journal portion4a having a gear 30 which is secured thereto and which is in meshingengagement with a driving helical gear 6 affixed to a shaft 32 of adriving electric motor which is mounted on a support 34 of the base 22.

In accordance with the invention sensing and control means in the formof a scanner or sensing element 8, a control device such as a dataprocessing unit and the electric motor 5 are provided for accuratelycontrolling the position of the rollers 3 and 3' in respect to aselected centerline position so that the slotted cylinder 2 may have itsslotted seam 9 centered in the nip 24 below the electron beam 1continuously during the welding operation.

The electrically energized sensors such as photocell elements 8a, 8b ofthe scanner 8 are arranged over the slot 9 of the slotted cylinder 2,and they are located to indicate any variations in centering between thetwo opposite edges 11, 11 of the slotted cylinder during the feeding ofthe slotted cylinder into the nip 24 between the rollers 3 and 3'. Apreselected distance such as the distance a is maintained between thesensors and the edges 11, 11 and 3' measured reactions of the sensorsare fed to the control unit or data processing unit 10. The control 10is arranged so that the shifting of the edges into a position at whichthey are picked up by one or the other of the sensors which provide anelectrical control pulse to the motor 5 to drive the motor in adirection and an amount to produce a rotation of bracket with theforming rollers 3 and 3' by an amount to restore the slotted cylinder 2to a centered position in respect to the welding device 28.

METHOD OF OPERATION operation:

A sheet of material 12 is fed in a direction of the arrow A and itssides are formed inwardly to form a cylindrical element 2 having alongitudinally extending slot 9. The cylindrical slotted tube 2 is fedbetween the rollers 3 and 3' and the slot 9 is centered in respect to awelding device 28 so that an electron welding beam 1 may be preciselypositioned in respect to the edges 11, 11'. The cylindrical member 2 ispressed together and it is welded along the seam line 14 to form afinished tube 13. During the welding process the electron beam 1 isalways centered above the slot 9 and forms a continuous seam line 14.The measuring sensors 8a and 8b are maintained at a distance a away fromthe respective strip edges 11 and 11 If there is deviation of the seam14 to the left or the right from the given centerline, the distance abetween the strip edges 11 or 11' and the measuring sensors 8a or 8b isincreased or decreased respectively. The sensors therefore transmit thismeasured increase or decrease with respect to a nominal preselectedcondition to the control unit 10 which in turn directs the motor 5 torun in a direction and in an amount to shift the forming rollers 3, 3until the seam line 14 is again in the middle between the weldingpressure rollers and exactly centered under the electron beam 1.

In the embodiment of the invention indicated in FIGS. 5 to 7, there isprovided welding means generally designated which includes an electrongun or welding device 28 which produces an electron beam 1', below whichthere is moved a workpiece 12' as in the other embodiment. The workpiece12' is formed into a tube with a longitudinally expending seam 13' as itis guided between a part of pressure welding rolls 3" and 3", which actto press the band edges 11', 11" against one another at the weldingpoint. The welding pressure roll 3" and 3" are arranged on a rocker 16which is pivotable about a longitudinal axis 17' of the tube 13. Thepivotal movement which, according to the usual seam migration may be upto approximately l5, is effected by means of a hydraulic power device18, which includes a fluid pressure cylinder 18a and a piston having arod portion 18b which is slidable inwardly and outwardly and whichconnects the rocker 16 through a lever 16a. The end position of therocker 16 is shown in dotted lines to the right of FIG. 6. In the sameposition the rocker is pivoted to the right by 7. l/2.

The hydraulic power device 18 is connected to the scanning means with acontrolling device such as the elements 8 and 10 of the embodiment ofFIG. 4. The controlling movement is controlled by the scanning elements8a and 8b as shown in FIG. 4, which are located on each side of theslots 9 in a position above the slot. They transmit the data of the slotcourse relative to the ideal of central run continuously to the dataprocessing system 10 as shown in FIG. 4 and this controls the powerdevice 18.

The rotation of the rocker 16 with the pressure forming rollers 3" and3" causes the workpiece to be twisted about its longitudinal axis 17 inthe same proportion of movement as the instantaneous seam migration butin the opposite direction of rotation. In order to insure that thisrotatable movement of the rollers occurs reliably at all times therollers are mounted on the rocker 16 together with a second pressureroll pair 19, 19. The second pressure roller pair acts to press the bandedges 11' against one another and consequently, firmly grips theworkpiece 13'. When a program is to be changed, of course, both pressureroll pairs 3" and 3" and 19 and 19' must be exchanged. Since thedistance of the rolls 3" and 3" and 19 and 19' from the workpiece axis17 is different, their bearing pedestals 40 and 41, which are carried onthe rocker 16, are mounted for displaceable movement in swallowtailguides 41.

The rocker 16 is mounted coaxially with the workpiece axis 17 inantifriction bearings 42 on bushings 43 which have bores 44 throughwhich a workpiece 13' runs with spacing. The bushings 43 are fitted inbearing pedestals 45 which are displaceable on rails 46 in the directionof the workpiece axis 17. The construction is such that the rocker 16can be introduced into the production line and removed therefrom withlittle expenditure of time.

In some instances, it is desirable that the band edges 11 and 11' bescanned by others means, for example, by pneumatically operable oroptically operable scanning devices.

What is claimed is:

1. A device for forming welded tubes including forming means for forminga sheet into a tubular element having a longitudinal slot definedbetween edges of the formed sheet, electric sensing means including aseparate sensor overlying but not contacting each edge of the formedsheet in a position to sense the location of the edges of the sheet asit is formed into a tube, a control connected to said sensing means andsaid forming means and responsive to the sensed locations of the sheetfor shifting said forming means for varying the position of the edges asthey are moved into said forming means to maintain a centering thereofin order to precisely position the slot, and an electron welding deviceoverlying said tubular element and directing a precisely orientedwelding beam into the slot to weld the edges together.

2. A welding device comprising feeding and forming means for feeding asheet of material to form it into a slotted tube with spaced edgesdefining a longitudinally extending slot and including spaced rollersdefining a nip therebetween into which said tube is fed, welding meansforming a precisely positioned welding beam located above said nip in aposition to weld the edges together, mounting means mounting saidrollers for movement to vary the location of said nip, and contactlessscanning means including a separate sensor overlying each edge of saidtube at a spaced location before said nip in positions to sense thelocation of the edges of the sheet as it is formed into a tube, saidscanning means being operatively connected to said mounting means forshifting said mounting means in response to the sensed location of saidspaced edges to move the nip to maintain the centering of saidlongitudinal slot in respect to said welding beam during the feeding ofsaid sheet material.

3. A welding device, according to claim 2, wherein said mounting meanscomprises a rotatable bracket carrying said rollers, an electric motorconnected to said bracket for rotating said bracket for shifting saidrollers and the nip therebetween transversely in respect to thelongitudinal slot of the tube which is being formed.

4. A device, according to claim I, wherein said forming means comprisesa pressure roll set including spaced-apart first and second press rollsbearing against the workpiece on respective opposite sides, and meansmounting said first and second pressure rolls for combined pivotalmovement, said control including said mounting means.

5. A device, according to claim 4, including a rocker arm carrying saidfirst and second pressure rolls, and means mounting said rocker arm forpivotal movement with said rolls about an axis which is substantiallyparallel to the axis of the tubular element which is formed.

6. A device, according to claim 5, including a second pressure roll setincluding a third and fourth rolls on respective opposite sides of thetubular element being formed and engaged with the element to urge theedges thereof into engagement for welding, all of said rolls beingmounted on said rocker arm for pivotal movement with said am about anaxis substantially parallel to the axis of the tubular element beingformed.

7. A device, according to claim 6, wherein said control includes a fluidpressure operated piston and cylinder combination, connected to saidrocker arm for shifting said rocker arm with said rolls and inaccordance with the migration of the seam of said tubular element.

1. A device for forming welded tubes including forming means for forminga sheet into a tubular element having a longitudinal slot definedbetween edges of the formed sheet, electric sensing means including aseparate sensor overlying but not contacting each edge of the formedsheet in a position to sense the location of the edges of the sheet asit is formed into a tube, a control connected to said sensing means andsaid forming means and responsive to the sensed locations of the sheetfor shifting said forming means for varying the position of the edges asthey are moved into said forming means to maintain a centering thereofin order to precisely position the slot, and an electron welding deviceoverlying said tubular element and directing a precisely orientedwelding beam into the slot to weld the edges together.
 2. A weldingdevice comprising feeding and forming means for feeding a sheet ofmaterial to form it into a slotted tube with spaced edges defining alongitudinally extending slot and including spaced rollers defining anip therebetween into which said tube is fed, welding means forming aprecisely positioned welding beam located above said nip in a positionto weld the edges together, mounting means mounting said rollers formovement to vary the location of said nip, and contactless scanningmeans including a separate sensor overlying each edge of said tube at aspaced location before said nip in positions to sense the location ofthe edges of the sheet as it is formed into a tube, said scanning meansbeing operatively connected to said mounting means for shifting saidmounting means in response to the sensed location of said spaced edgesto move the nip to maintain the centering of said longitudinal slot inrespect to said welding beam during the feeding of said sheet material.3. A welding device, according to claim 2, wherein said mounting meanscomprises a rotatable bracket carrying said rollers, an electric motorconnected to said bracket for rotating said bracket for shifting saidrollers and the nip therebetween transversely in respect to thelongitudinal slot of the tube which is being formed.
 4. A device,according to claim 1, wherein said forming means comprises a pressureroll set including spaced-apart first and second press rolls bearingagainst the workpiece on respective opposite sides, and means mountingsaid first and second pressure rolls for combined pivotal movement, saidcontrol including said mounting means.
 5. A device, according to claim4, including a rocker arm carrying said first and second pressure rolls,and means mounting said rocker arm for pivotal movement with said rollsabout an axis which is substantially parallel to the axis of the tubularelement which is formed.
 6. A device, according to claim 5, including asecond pressure roll set including a third and fourth rolls onrespective opposite sides of the tubular element being formed andengaged witH the element to urge the edges thereof into engagement forwelding, all of said rolls being mounted on said rocker arm for pivotalmovement with said arm about an axis substantially parallel to the axisof the tubular element being formed.
 7. A device, according to claim 6,wherein said control includes a fluid pressure operated piston andcylinder combination, connected to said rocker arm for shifting saidrocker arm with said rolls and in accordance with the migration of theseam of said tubular element.